• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.208-208
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• 2022

Recently, the frequency of abnormal weather due to complex factors such as global warming is increasing frequently. From the past rainfall patterns, it is evident that climate change is causing irregular rainfall patterns. This phenomenon causes difficulty in predicting rainfall and makes it difficult to prevent and cope with natural disasters, casuing human and property damages. Therefore, accurate rainfall estimation and rainfall occurrence time prediction could be one of the ways to prevent and mitigate damage caused by flood and drought disasters. However, rainfall prediction has a lot of uncertainty, so it is necessary to understand and reduce this uncertainty. In addition, when accurate rainfall prediction is applied to the rainfall-runoff model, the accuracy of the runoff prediction can be improved. In this regard, this study aims to increase the reliability of rainfall prediction by analyzing the uncertainty of the Korean rainfall ensemble prediction data and the outflow analysis model using the Limited Area ENsemble (LENS) and the Grid based Rainfall-runoff Model (GRM) models. First, the possibility of improving rainfall prediction ability is reviewed using the QM (Quantile Mapping) technique among the bias correction techniques. Then, the GRM parameter calibration was performed twice, and the likelihood-parameter applicability evaluation and uncertainty analysis were performed using R², NSE, PBIAS, and Log-normal. The rainfall prediction data were applied to the rainfall-runoff model and evaluated before and after calibration. It is expected that more reliable flood prediction will be possible by reducing uncertainty in rainfall ensemble data when applying to the runoff model in selecting behavioral models for user uncertainty analysis. Also, it can be used as a basis of flood prediction research by integrating other parameters such as geological characteristics and rainfall events.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.259-259
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• 2022

Soil salinity is a major factor that reduces crop yields. The amount of soil affected by salinity is about 83 million hectares (FAO 2000), which is increasing due to the effects of climate change. In soybean [Glycine max (L.) Merr.], nutritional properties such as protein, starch, and sucrose content together with biomass and yield tends to reduce due to excessive salt. As a result of QTL mapping using the 169 F_2:3 population from the KA-1285 (salt-tolerant) × Daepung (salt-sensitive) in a previous study, two major QTLs (Gm03_39796778 and Gm03_40600088) related to salt tolerance were found on chromosome 3. In this study, the CDS region of the Gmsalt3 gene was analyzed using the ABI 3730x1 DNA Analyzer (Macrogen, Korea). The sequence of Gmsalt3 gene in KA-1285 was compared with Williams 82.a4.vl and PI483463 (Glycine soja). Two transversions were found at exon6 in KA-1285 and PI483463. Currently, whole genome sequencing and variation analysis using the Illumine Novaseq 6000 machine (Illumina, USA) are in progress. The results of this study can provide useful molecular markers for the selection of salt-tolerant soybeans and can be used as basic data for future salt-tolerant gene research.

• 한국농공학회논문집
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• 제66권1호
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• pp.49-66
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• 2024

Extreme rainfall will become intense due to climate change, increasing inundation risk to agricultural land. Hydrological and hydraulic simulations for the entire watershed were conducted to analyze the impact of climate change. Rainfall data was collected based on past weather observation and SSP (Shared Socio-economic Pathway)5-8.5 climate change scenarios. Simulation for flood volume, reservoir operation, river level, and inundation of agricultural land was conducted through K-HAS (KRC Hydraulics & Hydrology Analysis System) and HEC-RAS (Hydrologic Engineering Center - River Analysis System). Various scenarios were selected, encompassing different periods of rainfall data, including the observed period (1973-2022), near-term future (2021-2050), mid-term future (2051-2080), and long-term future (2081-2100), in addition to probabilistic precipitation events with return periods of 20 years and 100 years. The inundation area of the Aho-Buin district was visualized through GIS (Geographic Information System) based on the results of the flooding analysis. The probabilistic precipitation of climate change scenarios was calculated higher than that of past observations, which affected the increase in reservoir inflow, river level, inundation time, and inundation area. The inundation area and inundation time were higher in the 100-year frequency. Inundation risk was high in the order of long-term future, near-term future, mid-term future, and observed period. It was also shown that the Aho and Buin districts were vulnerable to inundation. These results are expected to be used as fundamental data for assessing the risk of flooding for agricultural land and downstream watersheds under climate change, guiding drainage improvement projects, and making flood risk maps.

• Steel and Composite Structures
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• 제51권1호
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

• 지질공학
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• 제34권1호
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• pp.51-65
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• 2024

산사태는 전 세계적으로 매년 큰 재산 피해를 야기하는 자연 재해로 알려져 있다. 국내에서도 기후 변화의 영향으로 산사태 피해가 증가하는 경향을 보이고 있으며, 이로 인한 피해를 줄이기 위해서는 산사태를 증가시키는 인자들을 파악하는 것이 중요하다. 따라서 본 연구는 충청북도 충주시에서 발생한 산사태 피해에 영향을 미치는 변수들의 중요도를 평가하기 위해 랜덤포레스트 모델을 활용하여 14개의 인자들 사이의 중요도를 분석하였다. 연구 결과, 모델의 성능은 AUC가 0.87로 높은 정확도를 보이며, 변수 중요도는 경사 방향, 경사, 계곡까지의 직선 거리, 고도 순으로 정해졌으며, 이는 경사방향과 경사 등의 지형인자가 암종과 유효토심과 같은 지질과 토양인자보다 산사태 피해에 더 큰 영향을 미친다는 것을 시사한다. 이 연구 결과는 산사태 피해 예측지도의 제작 및 산사태 피해 감소에 초점을 맞춘 연구에 기초 자료로서 활용될 수 있을 것으로 기대된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.170-191
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• 2024

The transmission of confidential data using cover media is called steganography. The three requirements of any effective steganography system are high embedding capacity, security, and imperceptibility. The text file's structure, which makes syntax and grammar more visually obvious than in other media, contributes to its poor imperceptibility. Text steganography is regarded as the most challenging carrier to hide secret data because of its insufficient redundant data compared to other digital objects. Unicode characters, especially non-printing or invisible, are employed for hiding data by mapping a specific amount of secret data bits in each character and inserting the character into cover text spaces. These characters are known with limited spaces to embed secret data. Current studies that used Unicode characters in text steganography focused on increasing the data hiding capacity with insufficient redundant data in a text file. A sequential embedding pattern is often selected and included in all available positions in the cover text. This embedding pattern negatively affects the text steganography system's imperceptibility and security. Thus, this study attempts to solve these limitations using the Part-of-speech (POS) tagging technique combined with the randomization concept in data hiding. Combining these two techniques allows inserting the Unicode characters in randomized patterns with specific positions in the cover text to increase data hiding capacity with minimum effects on imperceptibility and security. Format-preserving encryption (FPE) is also used to encrypt a secret message without changing its size before the embedding processes. By comparing the proposed technique to already existing ones, the results demonstrate that it fulfils the cover file's capacity, imperceptibility, and security requirements.

• 한국음향학회지
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• 제26권7호
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• pp.353-360
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• 2007

급속한 도시화와 인구밀도의 증가로 도시의 주거지역은 점점 고층화, 고밀화 되어가는 추세이다. 그로 인하여 인구의 공간적 집중으로 발생하는 교통수요를 감당하기 위하여 도시내부 도로는 점차 증가하였으며, 주거지역은 도로에 바로 인접하여 개발되고 있다. 이에 따라 도로에 연접한 주거지역의 도로교통소음 문제를 해결하기 위하여 방음벽에 의존하는 실정이었으나, 경관저해, 소음차단성능저해 등 다양한 역기능이 발생하고 있다. 본 연구에서는 방음벽의 역기능을 해소하고 바람직한 개선방안을 제시하기 위하여 도로변에 위치한 주거지역의 현장측정을 통하여 시뮬레이션의 정확도를 검증한 후 방음시설별 성능평가 및 전체 지역을 분석하였다. 그리고 개선방안으로 건축물의 배치형태 변화와 도로단으로부터의 이격거리를 20m 증가시켰다. 분석 결과 도로변과 평행한 공동주택의 피해가 가장 심각하였고, 시설별 분석에서는 방음벽의 성능이 우수하였으며, 건물 배치형태는 $30^{\circ}$ 배치가 우수하며, 이격거리가 증가함에 따라 교통소음이 감소하는 것으로 나타났다.

• 대한영상의학회지
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• 제81권2호
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• pp.365-378
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• 2020

목적 본 연구는 gadoxetic acid 조영증강 간 자기공명영상에서 T1 이완시간이 만성간질환을 가진 환자에서 간섬유화의 발견과 병기설정에 유용한지 알아보고자 한다. 대상과 방법 국소간병변이 의심되는 103명 환자들이 간 자기공명영상과 Fibroscan을 시행하였다. Fibroscan은 간섬유화의 정도를 분류하는 참조표준검사로 사용되었다. T1 이완시간은 조영제 주입 전(preT1)과 주입 20분 후(postT1), 그리고 이들 간의 T1 이완시간 감소율(rrT1)을 3 테슬라 자기공명영상의 횡단 3D VIBE 시퀀스 하에 측정하였다. Receiver operating characteristic (이하 ROC) 분석을 통해 간섬유화 병기설정을 위한 최적의 cut-off 값이 결정되었다. 결과 METAVIR score (F0-F4)에 따른 간섬유화 병기가 증가함에 따라, preT1과 postT1은 증가하였고, rrT1은 감소하였다. PreT1의 F2와 F3 사이(F2, 836.0 ± 74.7 ms; F3, 888.6 ± 77.5 ms, p < 0.05), postT1의 F3와 F4 사이(F3, 309.0 ± 80.2 ms; F4, 406.6 ± 147.7 ms, p < 0.05), 그리고 rrT1의 F3와 F4사이(F3, 65.4 ± 7.7%; F4 57.3 ± 11.4%, p < 0.05)에서 통계적 유의미한 차이를 보였다. ROC 분석은 preT1과 postT1의 병용검사가 간섬유화 병기설정에 있어 가장 유용한 검사라는 것을 보여준다. 결론 preT1과 postT1은 간섬유화 병기가 증가함에 따라 증가하며, T1 mapping이 gadoxetic acid 조영증강 간 자기공명영상에서 간섬유화 병기설정에 있어 유용한 보조적 시퀀스로 사용될 수 있다.

• 한국측량학회지
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• 제27권6호
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• pp.639-647
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• 2009

오늘날 신속한 정보화 사회의 정착에 따라 지형공간정보의 수요와 활용이 급격히 증가하고 있으며, 해마다 변화하는 지형공간자료의 최신성과 정확성을 충족시키기 위해 국가지리정보체계 구축사업이 활발히 진행되고 있다. 그 중에서도 최근 정부의 뉴딜녹색정책의 핵심인 4대강 살리기 사업, 국제 습지보전 협약인 람사르(Ramsar) 총회의 개최 등으로 어느 때보다 환경 분야에 대한 관심이 높아지고 있는 실정이다. 한편, 낙동강 하구 지역은 습지는 물론 환경 분야에서의 보전가치가 매우 높아 관련분야에서 다양한 연구가 진행되고 있다. 하지만, 이 지역은 인위적 개발과 자연 현상으로 인한 지형과 생태계의 변화가 급속히 진행되고 있으나 이러한 변화 모니터링의 기본자료인 지형 DB 구축은 매우 미흡한 실정이다. 본 연구에서는 이러한 현실을 감안하여 낙동강 하구에 속하는 을숙도 복원습지를 대상으로 항공 LiDAR 측량을 수행하여 3차원 지형도와 식생분류를 통한 습지 구분도를 제작하여 정밀 지형 DB를 구축하였다. 이러한 정밀 지형 DB는 향후 을숙도 복원습지의 체계적인 유지관리에 크게 기여할 것으로 사료된다.

• 원예과학기술지
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• 제34권3호
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• pp.472-487
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• 2016

This study aimed to determine the effects of floral fragrances on human brain waves and moods. A total of 44 subjects participated in this experiment. Group 1 consisted of 11 male and 14 female college students with a mean age of 24.5 years (${\pm}2.23$) and Group 2 consisted of 10 males and 9 females with a mean age of 54.3 years (${\pm}2.98$). Subjects were exposed to floral fragrances of Rosa hybrida, 'Hera' (hereafter referred to as "rose"), Cymbidium faberi (hereafter referred to as "orchid"), or odorless control flowers (hereafter referred to as "control"). Experiments took place in three rooms (rose, orchid, and control). Electroencephalographs (EEGs) were recorded during exposure to the odors and the data were processed using quantitative electroencephalographic (QEEG) techniques. The changing EEG patterns were analyzed by brain mapping and compressed spectral arrays, and the subjects' preferences (hedonic evaluations) were quantified with an A1 index. Increased activation of absolute alpha waves was verified on six of the eight EEG channels, with the right frontal and left occipital lobes exhibiting no changes and the left parietal region showing the greatest activation. According to the QEEG measurements in the electrode sites over the frontal, temporal, parietal, and occipital lobes, the strongest absolute alpha waves were induced in the parietal lobes, followed by the temporal lobes, with the other lobes showing no significant changes. On brain maps, the orchid fragrance induced greater absolute alpha and absolute mid-beta activities compared with the rose and control fragrances, and the rose fragrance induced high absolute mid-beta activation. To identify emotional responses to floral fragrances, the subjects were requested to fill in a questionnaire and the resulting odor-related emotional descriptors were analyzed using semantic differential and factor analysis. Principal component analysis identified "elegant" as the first principal component describing the floral fragrance, followed by "refreshing" and "aromatic." The subjects gave orchid higher scores for "elegant" and "refreshing," while finding rose more "aromatic." Differences in hedonic evaluation revealed by the A1 index appeared in the 65-115 sec range of scent exposure time. The subjects with ages of around 50 years showed olfactory preferences throughout the entire experimental time of 160 sec, most markedly in the later time segment (115-165 sec), showing an increasing preference with increasing exposure time. We conclude that rose fragrance can improve concentration by creating an aromatic environment conducive to a concentrated and calm state of mind, and orchid fragrance can make people feel pampered and relaxed by creating an elegant and refreshing environment.